Add atom for a janky event reported by SurfaceFlinger.

This atom is intended to be used to alert a Perfetto subscriber on a
subset of janky events. This is for experimenting tracing jank events
from dogfood so that we can improve issue detection.

Bug: 148543048
Test: builds
Change-Id: I368855e4045c78a0cb65041cca762f4d334de916